ui: add minimum amount for onramps

[Mateo-Soso]

📐 Scope & Requirements

In scope:

• Add funds flow (crypto and bank transfers) — surface a 1 USDC minimum to receive funds (except through OP mainnet).

Out of scope:

• Validation logic / blocking submission below $1 (this change is informational only).

Requirements:

• Add informational copy on both flows letting users know there is a 1 USDC minimum for receiving funds, make clear that this limit is in usdc so users have to send the equivalent in the currency they select (example 1500 ARS). If they send less, there is no problem; they will receive the whole amount after they send more than 1 USDC.
• Purely informational — no change to validation behavior or submit-state logic.

🎨 Design Tasks

• Define scope & requirements
• Benchmarking
• Explore concepts / ideation
• Create wireframes
• High-fidelity design
• Prototype / interactions
• Design review
• Handoff to engineering